The invention relates to an automated cell for handling of workpieces, having a working space having at least a loading space into which a workpiece carrier for receiving workpieces can be loaded from the outside, having a handling device with a first gripping device for receiving workpieces from the workpiece carrier and for transferring of workpieces within the working space, and having a gantry upon which a carriage having a second gripping device is displaceable for removing workpieces from the working space and transferring same to a machine tool assigned thereto, and for receiving workpieces from the machine tool, and for transferring same into the working space.
Such an automated cell is known from DE 197 20 906 A1.
The known automated cell comprises a closed working space within which a loading space is provided separated by a protective wall. Parts that are placed on workpiece carrier stacks can be transferred into the loading space by means of a stack-changing module. Within the working space a stack presentation device is provided which is adapted for moving workpiece carrier stacks into a waiting area and which is adapted for moving a workpiece carrier into a waiting position from which parts can be removed by means of a gripping device arranged displaceable and vertically movable on a gantry toward a machine tool associated thereto, while machined parts can be received from the machine tool and placed again on the workpiece carrier.
The known automated cell is particularly suited for high throughput within a series fabrication, wherein, due to workpiece carrier stacks within the working space and within the loading space, a high buffer action is reached along with a decoupling between the handling of parts within the working space and loading or removal of part carriers from the loading space. The known automated cell is thus particularly suited for large series production of large parts and can also be utilized for supplying several machining centers. On the other hand, the turning stand directs a certain breadth of the cell which cannot be totally utilized for a pallet width due to the turning circle. Also the loading device utilized within the working space is relatively complicated.
From DE 198 24 014 A1 another automated cell comprising a working space closed to the outside is known within which a loading device for receiving at least one part carrier is arranged displaceable in horizontal and in vertical direction. Parts can be transferred into and out of, respectively the working space by means of a feeding device which is, preferably, configured as a transfer carriage and which comprises a support for receiving a part carrier at working level. The workpiece carriers can be transferred into the working space through a loading aperture the opening and closing of which is controlled automatically.
With such an automated cell the required space may be held relatively small, however within the working space only complete workpiece carriers are moved, rather than single workpieces.
For certain manufacturing tasks, for instance in the manufacturing of injection pumps for the common rail technique the workpieces must be machined extremely precisely and must for instance be measured or subjected to a different operation step in the automated cell. Thus the workpieces must for instance be tilted in the automated cell, pre-measured, finally measured or subjected to a brushing or cleaning operation.
In particular due to the short machining time of small parts up to now for performing such supplementary tasks within the automated cell additional handling devices are necessary that work in parallel, to avoid that the pick-up and supplementary tasks within the automated cell lead to a deceleration of the working cycle of the machine tool supplied thereby.
Thus it is the object of the invention to provide an improved automated cell for handling of workpieces and an improved process for the handling of workpieces which avoid the drawbacks of the prior art to a considerable part. In particular, the automated cell shall have a simple and space-saving design and shall allow the feeding or removal, respectively, of workpieces into or out of, respectively, a machine tool associated thereto in the simplest possible way, while being sufficiently fast even with very small workpiece machining times.
This object is achieved in the automated cell mentioned at the outset according to the invention in that the handling device is configured as a two-dimensional gantry having a first linear axis extending in longitudinal direction within the working space and being coupled with a second longitudinal axis extending in transverse direction, wherein the first gripping device is received on one of the linear axes vertically displaceably, in that at least one supplementary station such as an aligning station, a pre-measuring station, a final measuring station, a tilting/reversing station, a cleaning station or a transfer space for the second gripping device provided, wherein the first gripping device is displaceable between the first workpiece carrier and at least one supplementary station, wherein the second gripping device is displaceable between at least one supplementary station and the machine tool, and wherein at least the linear axes of the two-dimensional gantry comprise a linear motor drive.
The object of the invention is thus completely achieved.
According to the invention by coupling a two-dimensional gantry, along which the first gripping device is displaceable in longitudinal and transverse direction of the working space as well as in vertical direction, with a gantry for tying to the machine tool, workpieces can be supplied to the machine tool in time within the working cycle given by the machine tool, and machined workpieces can be removed therefrom. In addition, also supplementary operations, such as aligning, pre-measuring, or final measuring can be performed without impairing the working cycle of the machine tool thereby. This is achieved substantially by driving the linear axes of the two-dimensional gantry by means of linear motor drives, thereby, due to the high operating speed of linear drives, providing sufficient time for performing supplementary functions without impairing the working cycle of the machine tool. The automated cell according to the invention has a particularly compact design, since no additional drives are necessary for such supplementary stations.
The object of the invention is further achieved by a process comprising the following steps:
transferring workpieces on a workpiece carrier into a loading space of a working space;
picking up workpieces from the workpiece carrier by means of a first gripping device between displaceable and transverse in longitudinal direction and in vertical direction of a two-dimensional gantry which comprises a first linear axis extending in longitudinal direction of the working space, and a second linear axis extending in transverse direction of the working space and being coupled with the first linear axis;
displacing the workpieces to a second gripping device being displaceable along a gantry which connects the working space with a machine tool allocated thereto which has a main time for machining a workpiece and an idle time for loading and unloading of workpieces;
within the main time transferring a workpiece by means of the second gripping device from the working space toward the machine tool;
within the idle time turning over the workpiece to the machine tool and receiving a machined workpiece from the machine tool;
within the main time displacing the workpiece received from the machine tool into the working space;
within the main time receiving a workpiece from the second gripping device by means of the first gripping device and displacing toward the workpiece carrier;
wherein the first gripping device within the main time turns over and receives workpieces between at least one supplementary station, such as an aligning station, a pre-measuring station, a final measuring station, a tilting/reversing station, a cleaning station or a support station, and between the workpiece carrier and vice versa.
In this way according to the invention the remaining part of the main time of the machine tool within which the workpiece is machined, is utilized not only for transport functions but also for performing supplementary functions.
In a further development of the automated cell the second gripping device is configured as a V-loader having two gripping units that are movable alternately on linear motion paths converging in a V-shaped manner into a predetermined point.
Thus it is made possible to receive machined workpieces and to supply workpieces for machining to the machine tool, even within a very short idle time of the machine tool. Such short idle times are particularly important with respect to small workpieces having a short main time. To further improve the velocity also with respect to very short idle times, it is advantageous to provide also the second gripping device with linear motor drives.
The first gripping device of the automated cell is suitably arranged on a carriage driven by one of the linear axes and comprises a vertical guidance along which a gripping element is received displaceable in vertical direction.
According to an additional advantageous design the workpiece carrier may be placed in a drawer that is arranged transferable into and out of the loading space.
Thereby a particularly simple and space-saving design of the automated cell is reached.
According to an additional improvement of this design two loading spaces, into which the workpiece carriers can be transferred, are arranged adjacent each other.
According to this feature switching from one workpiece carrier to another workpiece carrier is made possible within the working space without interrupting the handling operations.
According to an additional development of the invention three loading spaces are arranged adjacent each other for receiving workpiece carriers.
This feature offers the advantage to allow a space-specific operation, that is a placing of the workpieces after machining on their original position, even when the respective machine tool holds a plurality of workpieces, before these are unloaded, as for instance the case with circular cycled machines. In these cases it is not necessary to empty the machine tool completely, before machining the next workpiece carrier, since always two workpiece carriers are accessible for machining, while the third workpiece carrier can be loaded or unloaded, respectively, independent thereof.
According to a further advantageous development of the invention a cover is provided that is movable in the direction of the second linear axis for separating one of the loading spaces from the working space protected against contact when loading and unloading.
Thereby a separation of the loading space from the working space is made possible for loading and unloading in a particularly simple way, protected against contact, while simultaneously workpieces from the workpiece carrier or from another carrier can be machined.
According to an additional development of the invention one of the linear axes comprises at least two linear motor drives arranged parallel to each other, the sliders of which being movable together in synchrony, wherein at least one of the sliders comprises a hall sensor for sensing the inductor rail, the hall sensor being coupled with both linear motor drives for controlling same.
This design which is also protectable independent from the other features of the automated cell, allows a considerable simplification and a considerable reduction in cost when compared to prior art linear motor drives, since when utilizing two parallel linear motor drives for driving a common carriage, in the prior art two incremental scales, for instance two glass scales, were necessary for controlling both linear motor drives with the necessary accuracy in synchrony.
However, it was found that the preciseness of common hall sensors which is in the order of a hundredth of a millimeter, is sufficient to provide the synchronous driving of a common carriage for the handling operations in this context.
According to a preferred improvement of the invention also at least the gantry or one of the gripping device comprises a linear motor drive.
As far as also the remaining drives of the automated cell are configured as linear motor drives, the working speed can further be raised, whereby more time is provided for performing additional tasks within the automated cell, without impairing the working speed of the machine tool supplied thereby.
According to a preferred development of the process according to the invention the transfer of a workpiece between the workpiece carrier and the at least one supplementary station as well as the working operation performed on the latter, is performed within the main time.
According to an additional development of the process according to the invention a gripping device having at least two gripping units for each workpiece is utilized for at least one of the gripping device.
Herein preferably a V-loader is utilized as a gripping device, the loader comprising two gripping units that are alternately movable along linear motion paths converging in a V-shaped manner toward a predetermined point.
Alternatively, it would also be conceivable to utilize a H-shaped loader comprising two gripping units or an I-shaped loader comprising two gripping units received, for instance, on a rotation axis.
As mentioned already before, at least the linear axes of the two-dimensional gantry are preferably driven by a linear motor drive.
By these measures a particularly fast operation when handling workpieces is supported to allow a loading and unloading of workpieces and possible supplementary operations within the main time of the machine tool, even with very fast operating machine tools, without causing a waiting time of the machine tool.
It will be understood that the above-described features and those to be discussed below are applicable not only in the given combinations, but may be used in other combinations or taken alone without departing from the scope of the invention.